Flat grinding disc

ABSTRACT

A flat grinding dic includes a grinding layer comprising grain, binding agent and preferably active and/or inactive filler, and a securing layer of plastics material arranged on the grinding layer on the mounting side thereof and having therein securing means, for example screw-threaded bores. The securing layer comprises foamed plastics material which is foamed onto the grinding layer.

United States Patent Helletsberger et a]. [4 Nov. 4, 1975 [5 FLAT GRINDING DISC 2,552,485 5/1951 Howard 51/209 R x 5l 358 [75] Inventors: Harald Helletsberger, wane; 2x322 ig/mu" 51/206 N F x Helmlch Wilhelm Faidacher, 3,290,834 12/1966 Lindblad 51/206 R both of p; Ernst Gelssler, 3,395,417 8/1968 Matouka 5l/358 x Schwaz, allof Austria 7 z 3] Asslgnee Austria Primary Examiner-Donald G. Kelly Attorney, Agent, or Firm-Wenderoth, Lind & Ponack [22] Filed: May 31, 1974 [21] Appl. No.1 475,244

[57] ABSTRACT [30] Foreign Application Priority Data June 8, 1973 Austria 5106/73 A flat grinding dic includes a grinding layer comprising grain, binding agent and preferably active and/or [52] US. Cl 51/209 R; 51/206 NF inactive filler, and a securing layer of plastics material [51] Int. Cl. B24D 7/04 arranged on the grinding layer on the mounting side [58] Field of Search 51/209 R, 209 DL, 206 R, thereof and having therein securing means, for exam- 51/206 NF, 358, 378, 401, 407 ple screw-threaded bores. The securing layer comprises foamed plastics material which is foamed onto [56] References Cited the grinding layer.

UNITED STATES PATENTS 7/l936 Webster 51/209 R 4 Claims, 3 Drawing Figures US. Patent Nov. 4, 1975 Sheet 2 of2 3,916,580

FLAT GRINDING DISC BACKGROUND OF THE INVENTION The invention relates to a flat grinding disc having a grinding layer of grain, binding agent and preferably active and/or inactive filler, and a securing layer com prising plastics material, which is arranged on the grinding layer on the mounting side thereof and which receives securing means, for example screw-threaded bores.

Flat grinding discs of this kind are known and are used for example when manufacturing piston rings. The particular difference as regards a disc which is only mounted at its boss is that an equal and uniform pressure is applied to the material to be ground, irrespective of where it is positioned under the grinding disc, and in particular tilting of the grinding disc can occur.

For the purposes of mounting the grinding disc on the grinding machine, th previously known grinding discs.

of the above-mentioned type are provided on their mounting side with screw-threaded bushes.

These bushes can either be incorporated directly into the material of the grinding layer, or bushings of metal or plastics material with an internal screw-thread are embedded into the grinding disc on the mounting side thereof.

The disadvantages of the known construction are on the one hand that it is relatively expensive to manufacture and also that a not inconsiderable part of the costly grinding material is lost for use.

SUMMARY OF THE INVENTION It is therefore the object of the present invention to provide a grinding disc which on the one hand permits optimum utilisation of the grinding material and which on the other hand can be easily manufactured.

In accordance with the invention, this is achieved in' that the securing layer comprises foamed plastics material which is foamed onto the grinding layer.

It is also within the concept of the present invention for the plastics material of the securing layer to penetrate through a part of the grinding layer.

Obviously the securing layer can also be provided with projections on the face thereof towards the grinding layer, for better anchoring the securing layer in the grinding material.

A preferred embodiment of the invention provides that the plastics material of the securing layer bonds chemically to the binding agent of the grinding layer.

The contours of the securing layer can be the same as the contours of the grinding layer proper, that is to say, the grinding plate, but in many cases it will be sufficient for the securing layer to be formed as a circular ring which extends only over a part of the radial dimension of the grinding disc.

The flat grinding disc according to the invention also affords for example the advantage that the discs can be pre-fabricated from a grinding layer and .a securing layer, so that mass production on a correspondingly large scale can be effected, whereupon the threaded bores for securing the grinding disc to the machine can be provided individually for each machine after an order has been made.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is described in detail hereinafter with reference to the figures of the accompanying drawings, although the invention is not limited to the embodiments illustrated.

FIG. 1 is a plan view of a flat grinding disc according to the invention,

FIG. 2 is a view in cross-section taken along line 1-1 in FIG. 1, and

FIG. 3 is a plan view of a further embodiment according to the invention of a flat grinding disc.

DETAILED DESCRIPTION OF THE INVENTION As is particularly clearly seen from FIG. 2, the grinding member 1 proper comprises a grinding layer 2 comprising binding agent, grain and fillers as required, and a securing layer 3 of plastics material, which adheres to the grinding layer 2. The plastics securing layer 3 has a thickness somewhat thicker then the depth h of the threade'dbores 4 therein.

The threaded bores 4 can be drilled and cut in the securing layer 3, in known manner.

FIG. -3 shows an embodiment of the invention in which the securing layer 3 is only formed as a circular ring, and does not therefore cover the whole surface of the grinding layer 2.

4 The selection between the embodiments illustrated will depend in particular on the loading to which the grinding disc is to be subjected.

The securing layer 3 can be injected or foamed onto the grinding layer 2, but it can also be produced separately therefrom, and subsequently joinged thereto by an adhesive.

Polyurethane will be mentioned here as an example of a suitable plastics material, but there is no restriction to suitable foamable plastics material.

We claim:

I. A flat grinding disc comprising:

a rigid disc-shaped grinding layer of an abrasive material formed of grinding grain, binding agent and filler, said grinding layer having a planar grinding surface and an opposite planar mounting surface spaced from said grinding surface;

a rigid securing layer formed of a rigid foamed plastics material, said securing layer having opposite spaced planar surfaces;

said securing layer at a first of said planar surfaces thereof being foamed into and rigidly secured to said mounting surface of said grinding layer; and

said securing layer having at a second of said planar surfaces thereof securing means for securing said grinding disc to a planar grinding machine.

2. A flat grinding disc as claimed in claim 1, wherein said plastics material of said first surface of said securing layer penetrates through a part of said grinding layer.

3. A flat grinding disc as claimed in claim 1, wherein said securing layer is in the form of a ring of radial dimensions less than the radial dimensions of said grinding layer.

4. A flat grinding disc as claimed in claim 1, wherein said securing means comprises threaded bores formed in said rigid foamed plastics material. 

1. A flat grinding disc comprising: a rigid disc-shaped grinding layer of an abrasive material formed of grinding grain, binding agent and filler, said grinding layer having a planar grinding surface and an opposite planar mounting surface spaced from said grinding surface; a rigid securing layer formed of a rigid foamed plastics material, said securing layer having opposite spaced planar surfaces; said securing layer at a first of said planar surfaces thereof being foamed into and rigidly secured to said mounting surface of said grinding layer; and said securing layer having at a second of said planar surfaces thereof securing means for securing said grinding disc to a planar grinding machine.
 2. A flat grinding disc as claimed in claim 1, wherein said plastics material of said first surface of said securing layer penetrates through a part of said grinding layer.
 3. A flat grinding disc as claimed in claim 1, wherein said securing layer is in the form of a ring of radial dimensions less than the radial dimensions of said grinding layer.
 4. A flat grinding disc as claimed in claim 1, wherein said securing means comprises threaded bores formed in said rigid foamed plastics material. 